The purpose of this study is to evaluate improvement in balance after receiving physical therapy when augmented by CN-NINM than when augmented by a placebo (sham CN-NINM).

Inclusion Criteria:

1. Veteran or Servicemember
2. 18 to 50 years old
3. Sustained one or more mild traumatic brain injury (mTBI)s
4. Demonstration of balance deficits on the Sensory Organization Test (a composite score of 75 or less (1/3 sample) and 72 or less (2/3 sample))
5. Available for the duration of the study

Exclusion Criteria:

1. History of traumatic brain injury (TBI) of any severity other than mild TBI

2. Presence of active substance abuse condition

3. Any condition for which posturography is contraindicated (e.g. leg amputation or fracture)

4. Diagnosed neurological disorder with balance sequelae, other than TBI (e.g. Parkinson's disease, incomplete spinal cord injury, or Multiple Sclerosis)

5. Orthostatic hypotension as defined by:

   1. A systolic blood pressure decrease (from supine to sitting) of at least 20 mmHg
   2. A diastolic blood pressure decrease of at least 10 mmHg, or
   3. A pulse increase of 30 beats or more per minute with associated signs or symptoms of cerebral hypoperfusion

6. An implanted medical device

7. Pregnancy

8. Oral infection

9. Known transmissible disease (HIV, hepatitis, influenza, TB)

10. Exam signs of serious disorder other than mTBI as defined by facial asymmetry, hoarseness and dysarthria (e.g. tumor, stroke).